ERENNA REVISION 

Fig. 19 Parerenna emilyae. Nectophores. A., B. upper, C. lower, and D. 
lateral views. Scale 2 mm. 
NECTOPHORE. (Fig. 19). Eight fully developed and two developing 
nectophores were found with the specimen; plus a few nectophoral 
buds at the apex of the highly contracted nectosome. Mature 
nectophores were not dorso-ventrally flattened and measured up to 
13 mm in length and width and 6 mm in height, and had well 
developed tapering axial wings. The central thrust block was broad, 
but of little height. The only obvious ridges were the apico-laterals 
(Fig. 19A, B), running down from the apices of the axial wings 
toward the ostium, but petering out well above that level. Only by 
staining were the pairs of complete vertical lateral and incomplete 
infra-lateral ridges revealed. The latter did not form the lower 
margins of the lateral surface of the nectophore (Fig. 19D). Two 
small patches of cells were found on each side of the nectophore, just 
basal to the vertical lateral ridges, although for many nectophores 
they had been abraded away. In addition there were three distinct 
strips of small epidermal cells, one dorsal and two lateral, stretching 
up from the ostium; the lateral pair being more extensive and 
pronounced than the dorsal one. These were all believed to be sites 
of bioluminescence. Mouth plate absent. Ostiun opened basally. 
The nectosac was Y-shaped in the younger nectophores, but the 
median apical indentation was less pronounced in the larger ones, 
181 
Fig. 20 Parerenna emilyae. Bracts of A. the first and B. the second type. 
Scale 1 mm. 
and may disappear altogether; the nectosac then being T-shaped. 
There was a large muscle-free zone on the apical, adaxial part of its 
lower side. The pallial canal was quite long, extending from the base 
of the thrust block to beyond the point of origin of the pedicular 
canal. The long pedicular canal was inserted onto the nectosac either 
at the point of origin of the lateral radial canals, or slightly basal to 
it. On half of the fully developed nectophores there was a slight 
asymmetry in the origin of the lateral radial canals with either the left 
or the right branching off before the other. The dorsal and ventral 
canals were straight and ran directly to the ostial ring canal. There 
was, however, a slight loop in the lateral radial canals as they curved 
over onto the lateral surface of the nectosac slightly above its mid- 
height. These canals then curved down to the mid-level and continued 
to the ostial ring canal. 
SIPHOSOME. The remaining piece of siphosome was highly con- 
tracted, with four gastrozooids and four palpons still attached. There 
were no signs of any gonodendra. 
BRACTS. (Fig. 20). Twenty-two bracts, up to 9 mm in length, 
remain with the specimen. Two basic types, present in approxi- 
mately equal numbers, could be distinguished. The first (Fig. 20A) 
was longer, but narrower, than the second (Fig. 20B). Both types 

Fig. 21 Parerenna emilyae. A. Gastrozooid. Scale 1 mm. B. Tentillum and C. Palpon. Scales 0.5 mm. 
